Risk factors

Most congenital heart defects result from problems early in your child's heart development, the cause of which is unknown. However, certain environmental and genetic risk factors may play a role. They include:

Rubella (German measles). Having rubella during pregnancy can cause problems in your baby's heart development. Your doctor can test you for immunity to this viral disease before pregnancy and vaccinate you against it if you aren't immune.

Diabetes. Having this chronic condition may interfere with the development of the fetus's heart. You can reduce the risk by carefully controlling your diabetes before attempting to conceive and during pregnancy. Gestational diabetes generally doesn't increase your baby's risk of developing a heart defect.

Medications. Certain medications taken during pregnancy may cause birth defects, including congenital heart defects. Give your doctor a complete list of medications you take before attempting to become pregnant.

Drinking alcohol during pregnancy. Avoid alcohol during pregnancy because it increases the risk of congenital heart defects.

Smoking. Smoking during pregnancy increases the likelihood of a congenital heart defect in the baby.

Heredity. Congenital heart defects appear to run in families and are associated with many genetic syndromes. Many children with Down syndrome — which is caused by an extra 21st chromosome (trisomy 21) — have heart defects. A missing piece (deletion) of genetic material on chromosome 22 also causes heart defects.

Genetic testing can detect such disorders during fetal development. If you already have a child with a congenital heart defect, a genetic counselor can estimate the odds that your next child will have one.

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